The invention relates to a method for adjusting the attitude (e.g. tilt and shift) of a rotation-symmetrical workpiece having an arcuate upper surface in a metrological apparatus, as well as a metrological apparatus for performing said method.
U.S. Pat. No. 4,731,934 A describes a metrological apparatus with a workpiece support that can be rotated about an rotary axis. For performing a measurement, the workpiece support is rotated with the workpiece arranged thereon. In conjunction with this, it is important for an accurate measurement that the axis of the workpiece be brought to coincide with the rotary axis. The metrological apparatus is disposed for measuring the dimensions of elongated workpieces having a cylindrical generated surface. A measurement is performed in circumferential direction of the workpiece in the direction of the rotary axis at a distance of the workpiece from the top and a distance of the workpiece from the bottom This allows the determination of the deviation of the axis of the workpiece relative to the rotary axis, and an appropriate positioning of the workpiece support can take place. This method is suitable only for workpieces displaying an adequately high generated surfaces in the direction of the rotary axis. Rotation-symmetrical bodies such as lenses, aspheres or the like cannot be adjusted in this manner.
A similar method has also been known, for example, from DE 101 02 383 A1 or DE 103 40 851 A1.
According to a method described in DE 10 2007 015 947 B4, a test measurement is performed prior to the actual measurement of a workpiece. In so doing, the zenith of the workpiece is determined, for example, based on several parallel profile measurements. The workpiece support is subsequently adjusted in such a manner that the zenith of the workpiece is located in the plane, in which the profile measurement is performed by means of the dial gauge of the metrological apparatus.
From WO 2009/124767 A1 a metrological apparatus is known, said apparatus comprising, for the determination of the axis of symmetry of a rotation-symmetrical workpiece, a special centering sensor that may be configured as an autocollimator. With the use of such an autocollimator, it is possible to determine the axis of symmetry of the spherical portion of the surface of the workpiece. The autocollimator detects the wobbling motion if the axis of symmetry of the workpiece does not coincide with a rotary axis of a rotationally driven workpiece support. This metrological apparatus thus requires a special, additional sensor that is not available in many universal metrological apparatus (shape measuring device and/or coordinate measuring devices).
DE 10 2012 023 377 B3 describes a method and an apparatus for measuring the position and adjustment of an asphere. With this method, a position value on the upper surface of the rotation-symmetrical workpiece is measured in several rotary positions at at least two different radial distances from the rotary axis, about which a workpiece is rotated. In other words, for each performed measurement, the measuring points are located on a circle around the rotary axis. If the axis of symmetry of the workpiece is not oriented exactly along the rotary axis, the measuring points describe a sine curve. It is possible, based on two or more such sine curves, to calculate the inclination of the axis of symmetry of the workpiece relative to the rotary axis, as well as the shift of the axis of symmetry relative to the rotary axis. This takes place, in particular, in that, initially, either the shift or the inclination is estimated using a measured sine curve and, with the use of this estimate, the respectively other value of the second measured sine curve is determined. These steps can be iteratively repeated until a sufficiently accurate determination has taken place and an appropriate adjustment can take place.
DE 196 51 232 C1 discloses a workpiece support with an adjustment assembly that can be activated in order to be able to adjust the position of a workpiece.